1. Field of the Invention
The present invention relates to a semiconductor package and a manufacturing method therefor, and more particularly, to a micromachine package with a hermetic cavity and a manufacturing method therefor.
2. Description of the Related Art
Micromachines, such as micromachine sensing elements and micromirrors, are well known. A micromachine includes a miniature moveable structure, such as a cantilevered beam, capacitive element, yoke and hinge. This micromachine usually cooperates with semiconductor elements, such as complimentary metal-oxide semiconductors (CMOS), to cause the movement of the moveable structure. Since the operation of the micromachine depends upon the moveability of the miniature moveable structure, it is critical that the package, which includes the micromachine, does not contact the miniature moveable structure in any manner.
Many micromachine packages have been disclosed in prior art, such as that disclosed in U.S. Pat. No. 6,415,505, which is incorporated herein by reference. Referring to FIG. 1, it depicts a micromachine package 10 in prior art. The micromachine package 10 includes a micromachine chip 14 with a moveable structure 16 which is disposed on a substrate 20 and electrically connected to the substrate 20 by way of bonding wires 18. A cap 12 covers the micromachine chip 14 for forming a cavity 30 surrounding the micromachine chip 14 such that the moveable structure 16 is freely moveable within the cavity 30. An encapsulant 24 encapsulates the micromachine chip 14, the substrate 20, the bonding wires 18 and the cap 12. The substrate 20 is further provided with a plurality of solder balls 22 for being electrically connected to an external print circuit board (not shown).
Further referring to FIG. 2, it depicts another micromachine package 10′ in prior art. The micromachine package 10′ is similar to the micromachine package 10, wherein the similar elements are designated with the same reference numerals. The micromachine chip 14 of the micromachine package 10′ is disposed on a die pad 32 of a lead frame 40 and the bonding wires 18 are connected to inner leads 34 of the lead frame 40. The lead frame 40 is further provided with a plurality of outer leads 36 for being electrically connected to an external print circuit board (not shown).
Referring to FIG. 3, it depicts a micromachine package 50 in prior art. The micromachine package 50 includes a micromirror chip 54 having moveable structures 55 and a CMOS chip 52 having electrodes 53 corresponding to the moveable structures 55. The micromirror chip 54 is disposed on the CMOS chip 52 and uniformly spaced apart from the CMOS chip 52 by spacers 56 to form a cavity 80 such that the moveable structures 55 cooperate with the electrodes 53 and freely move within the cavity 80. The CMOS chip 52 is electrically connected to a ceramic substrate 60 by bonding wires 58. The ceramic substrate 60 is provided with a dam 62 surrounding the CMOS chip 52, and a transparent lid 66 is fixed on the dam 62 by a seal 64.
As the need has arisen for lighter and more complex electronic devices, the velocity and the complexity of IC chip become more and more higher. Accordingly, a need has arisen for higher package efficiency. The semiconductor package manufactured at wafer level, for example, disclosed in U.S. Pat. Nos. 5,323,051, 5,925,936, and 6,004,867, provides many advantages, such as the ability of mass production, small package size, and reduced probability of contamination of wafer. Also, leadless chip carriers or leadless packages are emphasized because of their low inductance loss. However, there is no suitable semiconductor package or manufacturing method provided in the prior art for packaging semiconductors at wafer level as well as fulfilling the requirements of semiconductor packages.
Accordingly, there exists a need for a semiconductor micromachine package to be packaged at wafer level.